US5012338A - Teletext decoders - Google Patents

Teletext decoders Download PDF

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Publication number
US5012338A
US5012338A US07/534,775 US53477590A US5012338A US 5012338 A US5012338 A US 5012338A US 53477590 A US53477590 A US 53477590A US 5012338 A US5012338 A US 5012338A
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Prior art keywords
packet
received
teletext
data
numerical sequence
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US07/534,775
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English (en)
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Andrew K. Davies
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US Philips Corp
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US Philips Corp
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Assigned to U.S. PHILIPS CORPORATION, 100 EAST 42ND STREET, NEW YORK, NY 10017, A CORP. OF DE reassignment U.S. PHILIPS CORPORATION, 100 EAST 42ND STREET, NEW YORK, NY 10017, A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: DAVIES, ANDREW K.
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
    • H04N7/087—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only
    • H04N7/088—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only the inserted signal being digital
    • H04N7/0882—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical blanking interval only the inserted signal being digital for the transmission of character code signals, e.g. for teletext

Definitions

  • This invention relates to teletext decoders for use in a receiver which is suitable for receiving teletext transmissions of a type in which coded data pulses are transmitted in a television signal in television lines where no picture signals representing normal picture information are present e.g. in the field or vertical blanking interval (VBI).
  • VBI vertical blanking interval
  • teletext data is sub-divided into so-called data packets, there being, at the present time, up to 32 different data packets which are conveniently referred to as packets 0 to 31, respectively.
  • Packets 0 to 23 are display packets and are used to generate a teletext display on the screen of a television or other receiver.
  • the remaining data packets are commonly referred to as extension packets and do not form part of a teletext display page, but provide for certain enhancements of the basic display or provide other services such as the packet 31 commercial data service.
  • Each data packet is provided with its own unique row or packet address which allows them either to be transmitted in package sequence order or in any order, or row adaptive transmission may be used where only selected ones of the data packets are transmitted.
  • the teletext decoder is able to accurately identify each data packet from its row or packet address.
  • non-teletext "junk" data packets which appear to have a row or packet address which is the same as that of one of the valid data packets.
  • These non-teletext "junk” data packets are undesirable as they corrupt the valid data packets, and may appear, for example, as a row of unintelligible graphic signs on the display screen.
  • a teletext decoder for use in a receiver which is suitable for receiving teletext transmissions of a type in which coded data pulses in the form of teletext data packets are transmitted in a television signal in television lines where no picture signals representing normal picture information are present, the teletext decoder comprising first memory means for storing received data packets in a given numerical sequence order and characterised by means for indicating whether each data packet has been received in the correct given numerical sequence order, further means being provided for overwriting a data packet which is indicated as having been received out of its given numerical sequence order with a data packet having the same packet address which has been received in its correct given numerical sequence order.
  • a preferred form of teletext decoder is characterised by second memory means for storing the received data packets in the order they are received, and further means for transferring the data packets stored in the second memory means to the first memory means.
  • the means for indicating whether each data packet has been received in its correct given numerical order comprises third memory means associated with each of the data packets stored in the first memory means, in which case it may be arranged that the third memory means affords an indication of whether a corresponding data packet has been stored in the first memory, whether that data packet was received in the correct given numerical sequence order, or whether that data packet was received out of its correct given numerical sequence order.
  • a subsequent packet having an apparent valid packet address which corresponds to that of a packet already stored in its correct given numerical sequence may be rejected.
  • a method of processing a received teletext transmission of a type in which coded data pulses in the form of teletext data packets are transmitted in a television signal in television lines where no picture signals representing normal picture information are present comprising the step of storing received data packets in a given numerical sequence order and being characterised by the steps of indicating whether each data packet has been received in the correct given numerical sequence order, and overwriting a data packet which is indicated as having been received out of its given numerical sequence order with a data packet having the same packet address which has been received in its correct given numerical sequence order.
  • FIG. 1 is a block schematic diagram of a teletext decoder in accordance with the present invention.
  • FIG. 2 shows diagrammatically parts of the memory M2 of FIG. 1 in greater detail.
  • FIG. 1 of the drawings there is shown a block schematic diagram of a teletext decoder which comprises an antenna A for receiving a teletext transmission, the antenna A being connected to a television tuner T (typically a Philips Components tuner unit type U744) which affords an output to an intermediate frequency stage IF (typically a Philips Components integrated circuit type TDA 2541).
  • the demodulated video signal VS from the intermediate frequency stage IF is applied to a video processing circuit VP (typically a Philips Components integrated circuit type SAA 5231) which performs, among other things, data slicing for retrieving serial teletext data pulses D from the video signal VS.
  • VP typically a Philips Components integrated circuit type SAA 5231
  • the video processor VP also produces data clock pulses C and line sync pulses S from the video signal VS
  • the data pulses D together with the clock pulses C and line sync pulses S are fed to a data acquisition and control circuit DAC, which is preferably a Philips Components integrated circuit type SAA 5250.
  • the data acquisition and control circuit DAC operates on the serial teletext data pulses from the video processor VP and converts them into parallel data bytes which are stored in a dedicated first-in, first-out random access memory (typically of 2K ⁇ 8 bit) M1, via a multi-bit address and data bus B1.
  • the data acquisition and control circuit DAC is operated under the control of a microcontroller MC (typically an Intel type 8031) via a multi-bit address and data bus B2 which is itself interconnected with a programmable peripheral interface PPI (typically an Intel type 8255) and a main (random access) memory (typically a 32K ⁇ 8 bit) M2 via a further multi-bit address and data bus B3. Buses B2 and B3 can be common.
  • the programmable peripheral interface PPI affords access to a compatible personal computer PC (typically an IBM PC) via a multi-bit address and data bus B4, the computer PC controlling the display of the received teletext data.
  • the data bytes corresponding to the received teletext information are output from the data acquisition and control circuit DAC and stored in the memory M1. Once every vertical blanking interval (VBI) period the contents of the memory M1 are transferred, under the control of the microcontroller MC, to the main memory M2.
  • VBI vertical blanking interval
  • FIG. 2 of the drawings the memory M2 of the teletext decoder of FIG. 1 is shown diagrammatically in greater detail.
  • a portion of the main memory M2 is used as a raw data buffer (RDB) which typically consists of 100 to 200 rows, numbered RD0 to RDn, each of 42 bytes, each row of which has two bytes assigned to the magazine and row addresses whilst the remaining bits are arranged to store all the bytes relating to a particular data packet, it being recalled that there are typically up to 32 different data packets, each of which is numbered from 0 to 31.
  • RDB raw data buffer
  • the data packets of the received teletext data are stored in the buffer RDB in the order that they are received as raw data.
  • the data packets stored in the buffer RDB are transferred to a reformatting buffer (RB) which also forms part of the main memory M2.
  • the buffer RB consists of 32 rows, numbered R0 to R31, each of 40 bytes, into which the data packets stored in the buffer RDB are transferred.
  • data packets in the buffer RB are stored in correct numerical sequence, regardless of the order a particular data packet was received in.
  • data packet 0 is always stored in row R0
  • data packet 1 is stored in row R1 . . .
  • data packet 31 is stored in row R31, of the RB memory.
  • a status buffer SB Associated with the buffer RB is a status buffer SB, which typically consists of 32 bytes (each of 8-bits) B0 to B31, each byte of which corresponds to a respective row of the buffer RB.
  • the buffer SB bytes B0 to B31 are used to indicate the status of the data packet which is stored in the corresponding row of the buffer RB.
  • all the memory bytes will be set to zero to indicate that no relevant data packets are stored in the buffer RB.
  • the corresponding buffer SB byte is set to "1".
  • the corresponding buffer SB byte is set to "2".
  • the valid data packet 1 will be stored in row R1 of the buffer RB and the corresponding buffer SB byte B1 will be set to "1" to indicate that it had been received in sequence.
  • the non-teletext "junk” data packet 6 will be stored in row R6 of the buffer RB, but the corresponding buffer SB byte B6 will be set to "2" to indicate that it had been received out of sequence (and might therefore be a non-teletext "junk” data packet).
  • the status of the corresponding buffer SB byte is read-out and if it had been set to "2" (indicative of an out of sequence data packet) then if the subsequent data packet had been received in sequence, it is caused to overwrite the data packet stored in the respective row of the buffer RB.
  • a data packet 6 is subsequently received in its correct numerical sequence, i.e. after data packet 5, it is written into row R6 of the buffer RB in place of the original, out of sequence, data packet.
  • the status byte will return to "1".
  • non-teletext "junk” data packets are periodically replaced by correspondingly numbered valid data packets, so alleviating the problem of non-teletext "junk” packets.
  • a packet is received in its correct numerical sequence and stored in its correct position in the buffer RB, the subsequent reception of a non-teletext "junk” packet appearing to present the same address is ignored as the status "1" in buffer SB for that packet address shows that a valid packet has already been received.
  • the aforedescribed arrangement was based on the assumption that the teletext data packets were transmitted in the correct numerical sequence. If this is not the case and the data packets are transmitted out of strict numerical sequence, or row adaptive transmission is used, the buffer SB has no affect save to warn of possible non-teletext "junk" packets.
  • extension packets 26, 27 and 28 may be transmitted immediately after packet 0 and prior to sequential packets 1 to 23.
  • the required storage order in buffer RB can be that of transmission so that the buffer contains in sequence R0, R26, R27, R28, R1, R2, R3, etc.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Television Systems (AREA)
US07/534,775 1989-06-16 1990-06-07 Teletext decoders Expired - Lifetime US5012338A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8913903 1989-06-16
GB8913903A GB2233191A (en) 1989-06-16 1989-06-16 Teletext decoders

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US5012338A true US5012338A (en) 1991-04-30

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US07/534,775 Expired - Lifetime US5012338A (en) 1989-06-16 1990-06-07 Teletext decoders

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US (1) US5012338A (de)
EP (1) EP0403004B1 (de)
JP (1) JP3320712B2 (de)
DE (1) DE69011971T2 (de)
GB (1) GB2233191A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0564214A2 (de) * 1992-04-02 1993-10-06 Texas Instruments Incorporated Zeigen von digital kodierten Daten
US5459522A (en) * 1994-06-10 1995-10-17 Zenith Electronics Corporation Method for acquisition and display of an on-screen program guide
US5594736A (en) * 1993-12-24 1997-01-14 Sharp Kabushiki Kaisha Image-information storage regenerating device
US5596372A (en) * 1992-03-02 1997-01-21 Eeg Enterprises, Inc. Video signal data and composite synchronization extraction circuit for on-screen display
US5781245A (en) * 1995-02-02 1998-07-14 U.S. Philips Corporation Merging of video mosaic with teletext

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2257876B (en) * 1991-07-19 1995-04-26 Samsung Electronics Co Ltd Device for displaying teletext

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4653055A (en) * 1983-12-19 1987-03-24 Itt Industries, Inc. Method of correcting errors in bytes of teletext signals
US4679082A (en) * 1984-04-27 1987-07-07 Mitsubishi Denki Kabushiki Kaisha Code transmission system character broadcasting receiver
US4701914A (en) * 1984-09-26 1987-10-20 Kabushiki Kaisha Toshiba Apparatus for correcting cyclic code data stored in memory and method therefor
US4719510A (en) * 1985-10-16 1988-01-12 U.S. Philips Corporation Teletext decoders
US4910595A (en) * 1988-05-27 1990-03-20 U.S. Philips Corporation Teletext decoders
US4953022A (en) * 1988-05-27 1990-08-28 U.S. Philips Corporation Teletext decoders
US4963968A (en) * 1988-05-27 1990-10-16 U.S. Philips Corporation Method and apparatus for validating teletext data

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2180127B (en) * 1985-09-04 1989-08-23 Philips Electronic Associated Method of data communication

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4653055A (en) * 1983-12-19 1987-03-24 Itt Industries, Inc. Method of correcting errors in bytes of teletext signals
US4679082A (en) * 1984-04-27 1987-07-07 Mitsubishi Denki Kabushiki Kaisha Code transmission system character broadcasting receiver
US4701914A (en) * 1984-09-26 1987-10-20 Kabushiki Kaisha Toshiba Apparatus for correcting cyclic code data stored in memory and method therefor
US4719510A (en) * 1985-10-16 1988-01-12 U.S. Philips Corporation Teletext decoders
US4910595A (en) * 1988-05-27 1990-03-20 U.S. Philips Corporation Teletext decoders
US4953022A (en) * 1988-05-27 1990-08-28 U.S. Philips Corporation Teletext decoders
US4963968A (en) * 1988-05-27 1990-10-16 U.S. Philips Corporation Method and apparatus for validating teletext data

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
"Broadcast Teletext Specification" by British Broadcasting Corp., Independent Broadcasting Authority and British Radio Equipment Manufacturers Association, Sep. 1976.
"Computer Controlled Teletext User's Manual" by Kinghorn; Mullard Application Laboratory Mitcham; Nov. 1, 1983.
Broadcast Teletext Specification by British Broadcasting Corp., Independent Broadcasting Authority and British Radio Equipment Manufacturers Association, Sep. 1976. *
Computer Controlled Teletext User s Manual by Kinghorn; Mullard Application Laboratory Mitcham; Nov. 1, 1983. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5596372A (en) * 1992-03-02 1997-01-21 Eeg Enterprises, Inc. Video signal data and composite synchronization extraction circuit for on-screen display
US5760844A (en) * 1992-03-02 1998-06-02 Eeg Enterprises, Inc. Video signal data and composite synchronization extraction circuit for on-screen display
EP0564214A2 (de) * 1992-04-02 1993-10-06 Texas Instruments Incorporated Zeigen von digital kodierten Daten
EP0564214A3 (de) * 1992-04-02 1994-04-06 Texas Instruments Inc
US5594736A (en) * 1993-12-24 1997-01-14 Sharp Kabushiki Kaisha Image-information storage regenerating device
US5459522A (en) * 1994-06-10 1995-10-17 Zenith Electronics Corporation Method for acquisition and display of an on-screen program guide
US5781245A (en) * 1995-02-02 1998-07-14 U.S. Philips Corporation Merging of video mosaic with teletext

Also Published As

Publication number Publication date
DE69011971D1 (de) 1994-10-06
JPH0332181A (ja) 1991-02-12
GB2233191A (en) 1991-01-02
EP0403004B1 (de) 1994-08-31
GB8913903D0 (en) 1989-08-02
JP3320712B2 (ja) 2002-09-03
DE69011971T2 (de) 1995-04-20
EP0403004A1 (de) 1990-12-19

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